Liner bolt and removal apparatus therefor

ABSTRACT

A liner bolt ( 1 ) for securing a liner to a mill, the liner bolt ( 1 ) comprising a head ( 3 ) and a shank ( 4 ) extending therefrom, the shank ( 4 ) having an external thread thereon, and having a bore ( 5 ) therein extending from its free end. A removal pin ( 2 ) is adapted to be inserted into bore ( 5 ) when liner bolt ( 1 ) is to be removed from the mill. Removal pin ( 2 ) is adapted to be struck by a moil ( 14 ).

TECHNICAL FIELD

The present invention relates to liner bolts and an apparatus forremoving the same from mills. In particular, the apparatus is an adaptorthat can be fitted to a liner bolt removal tool for removal of suchliner bolts.

BACKGROUND

Liner bolts are typically used to secure sacrificial liners to theinternal casing of mills used in the mining industry. The sacrificialliners are routinely replaced during maintenance of the mills. Typicallysuch mills may range in size from three metres to eleven metres indiameter and are lined with replaceable heavy steel segments attachedinternally to the mill casing by through bolting using liner bolts. Theliner bolts typically have a diameter of up to about 50 mm (2 inches).

In such applications, the bolts become corroded and clearances betweenbolts and holes become compacted with ore fines. This results indifficult bolt removal at liner removal time. As a result the many linerbolts that are utilised to attach the liners to the mill shell are oftenrequired to be freed manually by the use of large sledge-hammers. Thisis a difficult and time-consuming task that may result in injury to theworkers.

While it is well known to use percussive devices such as jack-hammersand hydraulically powered hammers to provide repetitive impacts for manyapplications, they are not able to be manually guided into alignmentwith wall mounted bolts and other components. The applications of jackhammers are limited as the hammering effect produced by an electricallyor pneumatically operated jack hammer does not provide the impact aswould be provided by a sledge hammer, for example.

In known hammering devices capable of delivering such impacts, a highreaction force is produced which necessitates that such devices becarried by articulating machines or be rigidly attached to some supportstructure. This reduces their versatility and makes them unsuitable formany applications. Furthermore, it is difficult to quickly andaccurately align such devices with the shank of a bolt or the like foreffecting ready removal thereof.

International publication WO97/26116 (Russell Mineral Equipment Pty Ltd)describes a hydraulic linerbolt removal tool. The hydraulic toolessentially comprises a housing having a moil mounted at the forward endand a hydraulic piston assembly reciprocally moveable along the hammeraxis between a striking position at which the piston assembly strikesthe impact delivery member and a retracted position remote from theimpact delivery member. A firing means is provided for hydraulicallyfiring the piston assembly from its retracted position to its strikingposition under the control of actuating means. A reactive body assemblyis moveable in the direction of the hammer axis by driving means towardsthe impact delivery member prior to operation of the firing meanswhereby the reactive body assembly may be energised by movement andsubsequently decelerated to substantially absorb the reaction generatedby firing the piston assembly. Recoil is thus reduced whereby theapparatus may be operated by hand with the apparatus being suspendedabout its centre of gravity at the work site.

U.S. Pat. No. 6,904,980 (Rubie) describes a pneumatic liner bolt removaltool that is operable from a conventional compressed air supply.

A disadvantage associated with using such prior art liner bolt removaltools to remove conventional liner bolts, is that it is necessary forthe operator of the removal tool be assisted by a workman who helpsalign the moil of the removal tool with the liner bolt. This is becauseeven though the removal tools are suspended, their size and weight makesthem difficult to handle and they obstruct the operator's view of thework area. The workman assisting the operator typically utilizes ahandheld moil guide as shown in FIG. 1 of this specification. Thisplaces the workman assisting the operator of the liner bolt removal toolat risk of injury, due to his proximity to the working end of the toolas it is aligned with the liner bolt.

Another disadvantage of removing liner bolts using these liner boltremoval tools is the damage caused to the mill casing in the area aroundthe bolt hole, as a result of misalignment.

The present invention seeks to overcome at least some of theabovementioned disadvantages.

SUMMARY OF INVENTION

According to a first aspect the present invention consists of a linerbolt for securing a liner to a mill, said liner bolt comprising a headand a shank extending therefrom, said shank having an external threadthereon, characterized in that said shank having a bore thereinextending from its free end.

Preferably in use, when said liner bolt is to be removed from said millin a first embodiment, a removal pin is inserted into said bore.

Preferably in use, said removal pin in is adapted to be struck by amoil.

Preferably, said moil is operably mounted to a liner bolt removal tool.

Preferably, said moil is housed within an adaptor mounted to said linerbolt removal tool, and said adaptor is adapted to slidably engage withsaid pin.

Preferably, when said liner bolt is to be removed from said mill in asecond embodiment, a moil is adapted to be inserted into said bore.

According to a second aspect the present invention consists of a hammeradaptor for a liner bolt removal tool, said adaptor adapted to be fittedto said tool in such a manner to shroud said moil, said adaptor slidablyengagable with a liner bolt and a removal pin, said liner boltcomprising a shank having a bore therein and said removal pin adapted tobe seated within said bore, said adaptor to guide said moil intostriking engagement with said pin.

Preferably, said hammer adaptor is length variable.

Preferably, said hammer adaptor comprises a first tubular member springloaded in a telescopic arrangement with a second tubular member.

According to a third aspect the present invention consists of a removalpin in combination with a predetermined liner bolt, said predeterminedliner bolt comprising a head and a shank extending therefrom, said shankhaving an external thread thereon, and said shank having a bore thereinextending from its free end, said removal pin having a first end adaptedto be inserted into said bore of said liner bolt, and a second endadapted to be struck by a tool when said removal pin is in engagementwith said liner bolt.

According to a fourth aspect the present invention consists of a linerbolt for securing a liner to a mill, said liner bolt comprising a headand a shank extending therefrom, said shank having an external threadthereon, said shank being of length such that when said bolt is securedto said mill, a substantial portion of said shank protrudes from saidmill, thereby allowing a hammer adaptor for a liner bolt removal tool toslidably engage with said shank

Preferably, said hammer adaptor is length variable.

Preferably, said hammer adaptor comprises a first tubular member springloaded in a telescopic arrangement with a second tubular member.

BRIEF DESCRIPTION OF DRAWINGS

In order that this invention may be more readily understood and put intopractical effect, reference will now be made to the accompanyingdrawings which illustrate a typical embodiment of the invention andwherein:

FIG. 1 is a partial perspective view of prior art liner bolt removaltool being used with a prior art hand-held guide to remove a prior artliner bolt.

FIG. 2 is a perspective view of a liner bolt and a removal pin thereforin accordance with a first embodiment of the present invention;

FIG. 3 is a perspective view of the liner bolt of FIG. 2, with theremoval pin engaged therewith.

FIG. 4 is a partial perspective view of a liner bolt removal tool fittedwith an adaptor for removal of a liner bolt of the type shown in FIG. 1.

FIG. 5 is a partial cross-sectional view of the liner bolt removal tooland adaptor shown in FIG. 4 set up to remove the liner bolt.

FIG. 6 is a partial cross-sectional view of the liner bolt removal tooland adaptor shown in FIG. 4 as the liner bolt is being removed.

FIG. 7 is a perspective view of the adaptor shown in FIG. 4.

FIG. 8 is a cut-away perspective view of the adaptor shown in FIG. 7.

FIG. 9 is a partial cross-sectional view of an alternative embodiment ofa moil set up to remove a liner bolt of the type shown in FIG. 1.

FIG. 10 is a partial cross-sectional view of a liner bolt in accordancewith a second embodiment of the present invention.

MODE OF CARRYING OUT INVENTION

FIG. 1 is a prior art liner bolt removal tool 10 that utilises ahand-held moil guide 30 to remove a conventional liner bolt from a linersecured to a mill casing.

FIGS. 2 and 3 depict a liner bolt 1 and a removal pin (drifter) 2 inaccordance with a first embodiment of the present invention. Liner bolt1 is adapted for securing a sacrificial liner to the internal casing ofa mill used in the mining industry.

Liner bolt 1 comprises an oval shaped head 3 and a shank 4 extendingtherefrom. Shank 4 is preferably threaded in a conventional manner toallow a fastening nut (not shown) to engage therewith. Liner bolt 1 alsocomprises a bore 5 that extends into shank 4 a short distance from itsfree end 6. Liner bolt 1 is made of a similar material used forconventional liner bolts.

Removal pin 2 comprises a first cylindrical end 7, a central portion 8and a second cylindrical end 9. The first cylindrical end 7 has adiameter smaller than the second cylindrical end 9. Central portion 8has a diameter substantially greater than both first and second ends7,9. Central portion 8 also has a flat face facing the direction towhich the first cylindrical end 7 extends. Pin 2 is preferably made of asubstantially hardened material and is reusable.

In use, liner bolt 1 secures a liner to a mill casing in a conventionalmanner, with the head 3 of liner bolt 1 located internally and shank 4projecting externally of the mill casing. In order to remove the linerbolt 4, the second cylindrical end 7 of pin 2 is fully inserted intobore 5 such that the flat face of central portion 8 abuts against thefree end 6 of shank 4. In order to remove the liner bolt 1, the secondcylindrical end 9 of pin 8 is preferably struck by the moil of a hammer.

The liner bolt 1 may be made in sizes to replace conventional linerbolts. In one particular size, the liner bolt 1 may have a shank 4 witha diameter of about 45 mm, and an overall length of about 300-350 mm.This size bolt may have a bore 5 of about 25 mm diameter and about 75 mmin length.

FIGS. 4, 5 and 6 depict a conventional liner bolt removal tool 10 fittedwith a hammer adaptor 11 used to remove liner bolt 1 from a liner 12 andmill casing 13, via removal pin 2. Adaptor 11, which has a spring-loadedtelescopic arrangement, is fitted to tool 10 with moil 14 extendingtherethrough.

As can be seen in FIG. 5, pin 2 is inserted into bore 5 of liner bolt 1.The free end of adaptor 11 is slid onto the shank 4 of liner bolt 1,such that the fore end of moil 14 of tool 10 is in contact with secondcylindrical end 9 of pin 2. Once the adaptor 11 is in place, the tool 11does not require additional operator guidance. In use, tool 10 isactivated by the operator (not shown), and moil 14 strikes pin 2, whichin turn urges both pin 2 and liner bolt 1 from liner 12 and mill casing13. Also, the pin 2 can be recovered and re-used.

FIGS. 7 and 8 depict hammer adaptor 11. The hammer adaptor 11 comprisesa first tubular member 17 spring loaded by spring 18 in a telescopicarrangement with a second tubular member 19. A flange 20 havingapertures 21, extends from an end of second tubular member 19. Theflange 20 allows adaptor 11 to be connected to a conventional liner boltremoval tool 10. Second tubular member 19 is fixed relative to tool 10,however during operation, as the tool 10 is fired, the overall length ofadaptor 11 is variable as first tubular member 17 slides relative to thesecond tubular member 19.

In an alternative embodiment as shown in FIG. 9, particularly suited towhere it is difficult to use a pin 2, a special purpose moil 14 a mayhave a pin end 15 adapted to engage directly with bore 5 of liner bolt1.

FIG. 10 depicts a liner bolt 101 in accordance with a second embodimentof the present invention. Liner bolt 101, is in effect as if the linerbolt 1 and pin 2 as shown in FIG. 5 are integrated together to form bolt101 having a shank 104.

This shank 104 has an external thread thereon, thereby allowing it to besecured to mill casing 13 in a like manner to bolt 1 shown in FIG. 5.However, in this embodiment the free end of shank 104 extends asubstantial length externally of the mill, thereby allowing the hammeradaptor 11 to slidably engage therewith. The hammer adaptor 11 beingfitted to a tool 10 carrying a moil 14, similar to that shown in thefirst embodiment.

Removal of the liner bolts 1 as described in the abovementionedembodiments not only minimises the risk of injury to workers, but mayresult in the actual knock out times being reduced by 40-60%, which is aconsiderable saving of downtime. Another advantage of liner bolt 1 andremoval pin 2 is that their use significantly reduces risk of damagingthe area around the bolt hole.

The term “comprising” (and its grammatical variations) as used herein isused in the inclusive sense of “having” or “including” and not in theexclusive sense of “consisting only of”.

1. A liner bolt for securing a liner to a mill, said liner boltcomprising a head and a shank extending therefrom, said shank having anexternal thread thereon, characterized in that said shank having a boretherein extending from its free end.
 2. A liner bolt as claimed in claim1, wherein in use, when said liner bolt is to be removed from said milla removal pin is inserted into said bore.
 3. A liner bolt as claimed inclaim 2, wherein in use said removal pin in is adapted to be struck by amoil.
 4. A liner bolt as claimed in claim 3, wherein said moil isoperably mounted to a liner bolt removal tool.
 5. A liner bolt asclaimed in claim 4, wherein said moil is housed within an adaptormounted to said liner bolt removal tool, and said adaptor is adapted toslidably engage with said pin.
 6. A liner bolt as claimed in claim 1,wherein in use when said liner bolt is to be removed from said mill amoil is adapted to be inserted into said bore.
 7. A hammer adaptor for aliner bolt removal tool, said adaptor adapted to be fitted to said toolin such a manner to shroud said moil, said adaptor slidably engagablewith a liner bolt and a removal pin, said liner bolt comprising a shankhaving a bore therein and said removal pin adapted to be seated withinsaid bore, said adaptor to guide said moil into striking engagement withsaid pin.
 8. A hammer adaptor as claimed in claim 7, wherein said hammeradaptor is length variable.
 9. A hammer adaptor as claimed in claim 8,wherein said hammer adaptor comprises a first tubular member springloaded in a telescopic arrangement with a second tubular member.
 10. Aremoval pin in combination with a predetermined liner bolt, saidpredetermined liner bolt comprising a head and a shank extendingtherefrom, said shank having an external thread thereon, and said shankhaving a bore therein extending from its free end, said removal pinhaving a first end adapted to be inserted into said bore of said linerbolt, and a second end adapted to be struck by a tool when said removalpin is in engagement with said liner bolt.
 11. A liner bolt for securinga liner to a mill, said liner bolt comprising a head and a shankextending therefrom, said shank having an external thread thereon, saidshank being of length such that when said bolt is secured to said mill,a substantial portion of said shank protrudes from said mill, therebyallowing a hammer adaptor for a liner bolt removal tool to slidablyengage with said shank.
 12. A liner bolt as claimed in claim 11, whereinsaid hammer adaptor is length variable.
 13. A liner bolt as claimed inclaim 12, wherein said hammer adaptor comprises a first tubular memberspring loaded in a telescopic arrangement with a second tubular member.